diff --git a/core/src/com/google/inject/internal/MoreTypes.java b/core/src/com/google/inject/internal/MoreTypes.java
index bd0f838..12a7625 100644
--- a/core/src/com/google/inject/internal/MoreTypes.java
+++ b/core/src/com/google/inject/internal/MoreTypes.java
@@ -329,13 +329,7 @@
 
     public ParameterizedTypeImpl(Type ownerType, Type rawType, Type... typeArguments) {
       // require an owner type if the raw type needs it
-      if (rawType instanceof Class<?>) {
-        Class rawTypeAsClass = (Class) rawType;
-        checkArgument(ownerType != null || rawTypeAsClass.getEnclosingClass() == null,
-            "No owner type for enclosed %s", rawType);
-        checkArgument(ownerType == null || rawTypeAsClass.getEnclosingClass() != null,
-            "Owner type for unenclosed %s", rawType);
-      }
+      ensureOwnerType(ownerType, rawType);
 
       this.ownerType = ownerType == null ? null : canonicalize(ownerType);
       this.rawType = canonicalize(rawType);
@@ -403,6 +397,16 @@
       return stringBuilder.append(">").toString();
     }
 
+    private static void ensureOwnerType(Type ownerType, Type rawType) {
+      if (rawType instanceof Class<?>) {
+        Class rawTypeAsClass = (Class) rawType;
+        checkArgument(ownerType != null || rawTypeAsClass.getEnclosingClass() == null,
+            "No owner type for enclosed %s", rawType);
+        checkArgument(ownerType == null || rawTypeAsClass.getEnclosingClass() != null,
+            "Owner type for unenclosed %s", rawType);
+      }
+    }
+
     private static final long serialVersionUID = 0;
   }